Asymmetric deflection systems for cathode ray tubes



United States Patent Inventor Tadao Urano Tokyo, Japan App], No. 816,757 Filed Apr. 16, 1969 Patented Dec. 29, 1970 Assignee lwatsu Electric Company LTD.

Suginami Ku, Tokyo, a corporation of Japan Priority Apr. 18, 1968 Japan No. 43/26104 ASYMMETRIC DEFLECTION SYSTEMS FOR CATHODE RAY TUBES 3 Claims, 7 Drawing Figs.

US. Cl 315/18, 313/77 Int. Cl H0lj 29/74 FieldofSearch 315/18;

[56] References Cited UNITED STATES PATENTS 2,075,142 3/1937 Schlesinger 313/77 2,600,463 6/1952 Bertein......... 315/18X 2,803,769 8/1957 McNaney 313/77 Primary Examiner-Rodney D. Bennett, Jr. Assistant Examiner-Brian L. Ribando Attorney-Chittick, Pfund, Birch, Samuels & Gauthier ABSTRACT: In an electrostatic type asymmetrical deflection system for cathode ray tubes comprising a pair of spaced apart parallel deflection plates for defining a passage for an electron beam and an accelerating means, sets of opposing electrodes are provided in parallel with the electron beam and substantially perpendicular to the deflection plates. One of the deflection plates and one set of electrodes close to the accelerating means are connected to a source of signal and the other deflection plates and the other set of electrodes are grounded.

ASYMMETRIC DEFLECTION SYSTEMS FOR CATHODE RAY TUBES BACKGROUND OF THE INVENTION This invention relates to improvements relating to an asymmetrical deflection system of a cathode ray tube. In a prior art asymmetrical deflection system of a cathode ray tube two parallel electrodes are provided one of which being grounded and the other supplied with signals. Further an accelerating electrode is provided in front of said two electrodes. With this type of asymmetrical deflection system the potential at the center of the deflection system is varied by the signals so that the unifonnity and linearity of the electron beam spot on the fluorescent screen of the cathode ray tube are impaired.

SUMMARY OF THE INVENTION It is therefore an object of this invention to eliminate the defect described above.

Briefly stated in accordance with this invention there is provided an asymmetrical deflection system for cathode ray tubes, comprising a pair of spaced apart parallel deflection plates defining a space through which an electron beam travels, an accelerating means and two sets of opposing electrodes extending in parallel to the electron beam and substantially perpendicular to the deflection plates. One of the deflection plates and one set of the electrodes close to the accelerating means are supplied with a signal voltage and the other deflection plate and the other set of electrodes are grounded.

BRIEF DESCRIPTION OF THE DRAWING The invention can be more fully understood from the following description when taken in conjunction with the accompanying drawing in which:

FIG. 1 diagrammatically shows one example of a prior art electrostatic type asymmetrical deflection system for use in cathode ray tubes;

FIG. 2 shows a perspective view of electrodes of the novel electrostatic type asymmetrical deflection system;

FIG. 3 diagrammatically shows the asymmetrical deflection system shown in FIG. 2;

FIG. 4 shows a perspective view of a modified electrode arrangement, and

FIG. 5 to 7 are diagrams to explain the principle of the operation of the asymmetric deflection system embodying this invention. DESCRIPTION OF THE PREFERRED EMBODI- MENTS Referring now to the accompanying drawing, FIG. 1 diagrammatically illustrates a prior art asymmetric deflection system for cathode ray tubes in which a pair of parallel electrodes A and B are disposed to define a passage for an electron beam not shown. One electrode A is grounded and the other B connected to a source of signal not shown. A grounded accelerating electrode C is provided at right angles with respect to electrodes A and B. As has been pointed out, in the asymmetrical deflection system of this construction there is a defect that the voltage of the center of the deflection system is varied by the signal to impair the linearity and uniformity of the spot on the fluorescent screen.

As shown in FIGS. 2 and 3, in accordance with this invention two sets of spaced apart opposing electrodes D and E are provided between electrodes A and B in parallel with the electron beam and perpendicular to electrodes A and B. These electrodes cooperate to define a passage of rectangular cross section for the electron beam. Electrode set D is connected to a source of signal, not shown, while the other electrode set E is grounded as shown in FIG. 3. FIG. 5F shows the voltage condition of various electrodes wherein represents the ground potential and V the signal voltage. To investigate the force acting upon the electron beam passing through the deflection system, FIG. SP is decomposed into FIGS. G, 5H and SI according to the theory of voltage superposition. In the following, the case wherein the voltage is positive will be considered,

but the case wherein the voltage is negative can be treated in the same manner. For the sake of description, effect upon the uniformity of the spot and that upon the linearity will be considered separately.

First, uniformalizing function of the spot is considered. Since FIG. 5G is a uniform deflection system, there is no problem. However, the arrangement shown in FIG. 5H results in a potential distribution as shown in FIG. 6 thus creating forces acting in the direction of the arrows. As a result, a circular electron beam is deformed into elliptical.

When taking cross sections, the arrangement shown in FIG. SI, results in potential distributions shown in FIGS. 7.] and 7K. As can be clearly noted from FIG. 7K, in the region K the electron beam has already been deflected to a considerable extent so that the electron beam will be subjected to upward forces, but the electron beam itself is not deformed substantially. However, in the region J, forces act inthe direction of arrows to elliptically deform the electron beam. As forces act in different ways for cases shown in FIGS. 5H and SI, by suitably proportioning and designing the construction shown in FIGS. 2 and 3 it is able to avoid deformation of the electron beam which enables unifonn diameter of the spot on the fluorescent screen of the cathode ray tube to be obtained.

Turning now to the uniformalizing function of linearity the speed of an electron beam passing through the deflection system shown in FIGS. 2 and 3 is accelerated by the arrangement of FIG. 5H, and as the accelerated beam is subjected to the action of the symmetrical deflection system shown in FIG. 5G its linearity will be impaired. Whereas, under conditions shown in FIGS. 7] and 7K, the directions of forces acting upon the electron beam are just opposite and hence directions in which the linearity varies are also opposite. Consequently, by a proper design of the length of electrodes D and E of FIG. 3 it is able to eliminate the changes in the linearity whereby it is possible to make uniform the linearity.

In the modified arrangement shown in FIG. 4, electrodes A and E are made integral and electrodes B and D are made integral. Like FIG. 3, electrodes A and E are grounded and electrodes B and D are connected to a source of signal (not shown).

Thus, in accordance with this invention, significant defects of the prior art electrostatic type asymmetrical deflection system, i.e. large nonuniformity and nonlinearity can be greatly improved.

Moreover, cathode ray tubes including the novel asymmetrical deflection system enable to eliminate one side of a vertical amplifier of the prior art oscilloscope or samploscope.

While the invention has been shown and described in terms of preferred embodiments thereof it should be understood that many changes and modifications will be obvious to one skilled in the art without departing from the true spirit and scope of the invention as defined in the appended claim.

I claim:

1. In an electrostatic type asymmetrical deflection system for cathode ray tubes, comprising a pair of spaced apart parallel deflection plates defining a space through which an electron beam travels and an accelerating means, the improvement which comprises two sets of opposing electrodes extending in parallel to said electron beam and substantially perpendicular to said deflection plates, to define a passage for said beam, one of said deflection plates and one set of said electrodes close to said acceleration means being supplied with a signal voltage and the other deflection plate and the other set of electrodes being grounded.

2. The electrostatic type asymmetrical deflection system according to claim 1 wherein said deflection plates and said two sets of opposing electrodes cooperate to define said passage as a space of rectangular cross section through which said electron beam travels.

3. The electrostatic asymmetrical deflection system according to claim 1 wherein one of said deflection plates and one set of said electrodes are made integral and the other deflection plate and the other set of electrodes are also made integral. 

